1. Field of the Invention
The present invention relates to a staged, fluidized bed distillation reactor. Such a reactor may be used for simultaneously performing distillation and heterogeneous catalysis to separate reactants from the product of the catalytic reaction. In a further aspect, the present invention relates to process for catalytically reacting and separating materials in a novel fluidized bed distillation reactor.
2. Description of the Prior Art
The reaction and separation of materials in a distillation reactor is generally known in the art. For example, the reaction of a stream of mixed olefins with methanol to form an ether which is removed from the remaining olefin stream in a distillation reactor is disclosed in U.S. Pat. Nos. 3,629,478, 3,634,534 and 3,634,535 to Haunschild. In the process of U.S. Pat. No. 3,629,478, a mixture of tertiary pentenes and linear pentenes is fed to a distillation column reactor. An alcohol is also fed to the reactor. The mixture of pentenes and alcohol is contacted with a heterogeneous catalyst in the reactor downcomers, to thereby catalytically react the tertiary pentene with the alcohol to form an ether. The ether is then fractionated from the linear pentenes in the reactor.
As explained in the '478 patent, the reaction of tertiary olefins with alcohols having 6 or less carbon atoms is equilibrium limited. This equilibrium limitation is overcome in the prior art by carrying out the reaction in a distillation reactor. When the ether is formed in the distillation reactor, it is relatively easy to fractionate the ether away from the olefins. In the distillation reactor the heavier or less volatile component, e.g., the ether, is constantly fractionated away from the reaction zone and the reaction does not reach equilibrium.
Although such prior art systems operate successfully, it is preferable that processes be undertaken in a vessel which has a relatively small volume, yet still provides the required catalyst volume and the vapor-liquid capacity required for distillation. In addition, the system should avoid bypassing of the vapor or liquid so that neither the catalytic reaction nor the vapor-liquid mass transfer efficiency is jeopardized.
Typically, the catalyst used in heterogeneous catalysis must be particulate to assure efficient reaction. However, beds of such small sized particulates make poor distillation column packing due to their low vapor capacity and high pressure drops across such beds. As noted above, the distillation reactors shown in the Haunschild patents employ beds of catalyst in the reactor downcomers. While this arrangement permits the process to be performed, the practical design of downcomers to convey liquid through the catalyst with the limited liquid head available can result in very inefficient use of the space within the distillation reactor.
A further example of a distillation reactor is set forth in U.S. Pat. Nos. 4,194,964 and 4,213,847 to Chen et al. In these patents, heavy petroliferous stocks are concurrently distilled and hydroprocessed for removal of sulfur, nitrogen and metals and are hydrocracked or otherwise hydroprocessed in a packed distillation column under hydrogen pressure.
In U.S. Pat. No. 3,506,408 to Kageyama et al, a multistage reaction apparatus is shown. The apparatus comprises a liquid feed inlet at the top of the apparatus, a gas inlet at the bottom of the apparatus and a plurality of perforated trays containing catalyst beds. The liquid passes downward through the catalyst on the trays and the gas zig-zags around the trays such that there is essentially no counter-current contact of liquid and gas within the catalyst beds, and very inefficient fractionation of vapor and liquid components in the desired manner.
It has been proposed in U.S. Pat. No. 4,215,011 to Smith, Jr., to contain particulate catalyst in an array of closed cloth pockets supported by wire mesh in a reaction-distillation column. Such an array has the disadvantage of being relatively difficult and expensive to construct and replace. Also, such a catalyst system would require restructuring of conventional distillation columns. Finally, the catalyst dispersion could not be uniform throughout the array, but rather is concentrated in the pockets. Therefore, very inefficient contacting of liquid and vapor with the catalyst will result causing very poor utilization of catalyst to achieve the desired chemical conversion.
Accordingly, it is an object of the present invention to provide, in the limited volume of a conventional distillation reactor, structures employing a particulate catalyst bed with high liquid and vapor capacity and low pressure drop.
It is another object of the present invention to provide an easily fabricated catalyst packing for a conventional distillation reactor.
It is another object of the present invention to provide a distillation reactor, with vapor and liquid flows facilitating high heterogenous catalytic reaction rates and mass transfer efficiency by providing intimate mixing of catalyst with the liquid and vapor.
It is a further object of the present invention to provide a process for reacting and separating material from a feedstream in a novel distillation reactor.
It is a still further object of the present invention to provide an improved process for separating non-tertiary olefins from tertiary olefins.
These and other objects and features of the invention will become apparent from the claims, and from the following description when read in conjunction with the accompanying drawings.